The present invention relates to semiconductor wafer processing equipment and, more particularly, to delivery systems for chemical vapors from liquid sources.
In the processing of semiconductor wafers, many processes require the delivery of gases into a processing chamber in which one or more semiconductor wafers are placed. Typically these gases at their sources are in the form of gases, such as nitrogen, oxygen, hydrogen, arsine, etc., in pressurized tanks. However, some processes use gases which are liquid at their sources. The liquid is heated to a vapor which is introduced into the processing chamber.
In U.S. Pat. No. 5,252,134, which issued on Oct. 12, 1993 to the present inventor, an integrated delivery system for chemical vapors from liquid sources was described. The described delivery system overcame many of the problems of older, more complex delivery systems which used a discrete bubbler unit or heated reservoirs. In these complex systems other discrete units, such as valves, pressure and mass flow controllers, and the feed line through which the chemical vapor passes, were connected between the bubbler or reservoir unit and the processing chamber. Each of the discrete units were often heated. In any case, problems arose with these complicated delivery systems, including condensation at the unheated or inadequately heated points of the system.
Nonetheless, while the described system overcame the problems of reliability and the consistency of performance in the older delivery systems, performance in the described system can still be improved. This is especially true for liquid sources containing silylation agents where very small variations in temperature and pressure in the delivery module of the chemical vapor have large effects on the results, such as the rate of reaction, thickness of deposited or grown film, etc.
The present invention offers improvements in the described delivery system which solves or substantially mitigates even very small variations in temperature and pressure in the delivery module of the chemical vapor.